Bandwidth-adjustable dual-passband filter

Abstract

A bandwidth-adjustable dual-passband filter comprises an input micro-strip, a band-pass sub-filter, a cascade micro-strip, an adjustable band-stop sub-filter and an output micro-strip, and is characterized in that the band-pass sub-filter and the adjustable band-stop sub-filter are connected together through the cascade micro-strip, the band-pass sub-filter is formed by cascading a 1 / 2 wavelength main transmission line and a 1 / 4 wavelength long-short line, and the output micro-strip is connected with the adjustable band-stop sub-filter through the cascade micro-strip. The adjustable band-stop sub-filter is formed by coupling a 1 / 4 wavelength main transmission line and a 1 / 2 wavelength resonator with a finger tip loaded with a variable capacitor, the working frequency of the adjustable band-stop sub-filter is located in a passband of the band-pass sub-filter, and the dual-passband function with the adjustable bandwidth is achieved; the dual-passband filter has the advantages that the working frequency of the adjustable band-stop sub-filter is located in the passband of the band-pass sub-filter, the dual-passband function is achieved, the variable capacitance of the 1 / 2 wavelength resonator with the variable capacitance loaded at the finger end in the adjustable band-stop sub-filter is adjusted according to frequency requirements, and the bandwidth adjustable function of the dual-passband filter is achieved.

Description

(I) TECHNICAL FIELD

[0001] The utility model relates to a kind of double-passband filters, especially a kind of bandwidth adjustable double-passband filter, and the present double-passband filter can be made of high-temperature superconducting film. (II) BACKGROUND

[0002] The filter has the important effects of frequency selection, frequency division and signal isolation. In a microwave communication system, the filter is widely used in the receiving and transmitting systems of signals. It not only selects useful signals from a large number of microwave signals in free space and suppresses spurious signals to avoid interference of noise signals outside the working frequency band on the receiver, thereby improving the signal-to-noise ratio of the system, but also limits the radiation signals of a high-power transmitter outside its working frequency band in the transmitter, filters the nonlinear signals generated by active devices. The filter plays a crucial role and even affects the performance of the microwave wireless communication system. With the development of modern microwave communication technology, the complexity and integration of communication system devices are gradually increasing. Single-passband filters cannot meet the application requirements of multi-band integration. Based on the application requirements of multi-band large flux in a communication environment, there is an increasing demand for double-passband microstrip filters with low loss, high suppression and wide passband. Wireless network applications combined with mobile communication have become a development trend, which greatly increases the application range of microwave double-passband filters. Therefore, double-passband filters have become important devices in wireless communication systems.

[0003] There are many types of double-passband filters, and the design methods are different. Traditional filters are obtained by connecting two single-passband filters in parallel. Double-passband response is achieved by designing port matching. This method is difficult to debug and is not easy to miniaturize. Secondly, a double-frequency resonator is designed, and an impedance transformer or electromagnetic coupling method is used for cascading to form a double-passband response. The design of this type of filter is complex, and it is difficult to implement products with high specifications. Although there are many types of existing double-passband filters, most of them are fixed-bandwidth and fixed-frequency double-passband filters. When only specific frequency signals within the working frequency range need to be suppressed, the bandwidth needs to be adjustable, and the overall working frequency range of the filter will not change. Therefore, how to design a double-passband filter with adjustable bandwidth and high performance has become a key issue. (III) UTILITY MODEL CONTENTS

[0004] The utility model aims at designing a kind of bandwidth adjustable double-passband filter, it has the characteristics such as small size, flexible design, transition band steep, is suitable for using high-temperature superconducting film with high quality factor to make.

[0005] The utility model discloses a technical scheme: a bandwidth adjustable double passband filter, including input microstrip, band pass sub filter, cascade microstrip, adjustable band elimination sub filter, output microstrip, its characterized in that, band pass sub filter and adjustable band elimination sub filter are connected together through cascade microstrip, and band pass sub filter is constituted by 1 / 2 wavelength main transmission line and 1 / 4 wavelength short circuit line cascade, and adjustable band elimination sub filter is constituted by 1 / 4 wavelength main transmission line and 1 / 2 wavelength resonator coupling of the 1 / 4 wavelength main transmission line and the variable capacitance of the finger end loading, and the 1 / 2 wavelength resonator of the variable capacitance of the finger end loading is constituted by 1 zigzag microstrip, 2 variable capacitances and ground microstrip, and the working frequency of adjustable band elimination sub filter is located in the passband of band pass sub filter.

[0006] The working mechanism of the double passband filter is as follows: the band pass sub filter and the adjustable band elimination sub filter are connected together through the cascade microstrip, the working frequency of the adjustable band elimination sub filter is located in the passband of the band pass sub filter, the passband of the band pass sub filter is divided into two passbands, the double passband function is realized, the variable capacitance of the 1 / 2 wavelength resonator of the finger end loading in the adjustable band elimination sub filter is adjusted according to the frequency requirement, the change of the capacitance value causes the change of the working frequency of the adjustable band elimination sub filter, and thus the bandwidth adjustable function of the double passband filter is realized.

[0007] The double passband filter is characterized in that the 1 / 2 wavelength main transmission line and the 1 / 4 wavelength short circuit line of the band pass sub filter are alternately connected in cascade, and the total number is 5-50.

[0008] The double passband filter is characterized in that the 1 / 4 wavelength main transmission line of the adjustable band elimination sub filter is connected together in cascade, the 1 / 2 wavelength resonator of the variable capacitance of the finger end loading is gap coupled with the 1 / 4 wavelength main transmission line, and the total number is 5-50.

[0009] The double passband filter is characterized in that the input microstrip is connected to one end of the band pass sub filter to produce direct excitation.

[0010] The double passband filter is characterized in that the output microstrip is connected to one end of the adjustable band elimination sub filter to produce direct excitation.

[0011] The double passband filter is characterized in that the input microstrip is connected to one end of the band pass sub filter to produce direct excitation. (Four) the drawing explanation:

[0012] Figure 1 is a structural schematic diagram of a bandwidth-adjustable dual-passband filter according to the present application. Figure 1 Figure 2 is a structural schematic diagram of a band-pass sub-filter of the bandwidth-adjustable dual-passband filter according to the present application. Figure 3 is a structural schematic diagram of an adjustable band-stop sub-filter of the bandwidth-adjustable dual-passband filter according to the present application.

[0013] Figure 4 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.3pF. Figure 2 Figure 5 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.1pF. Figure 6 is a structural schematic diagram of a bandwidth-adjustable dual-passband filter according to the present application.

[0014] Figure 7 is a structural schematic diagram of a band-pass sub-filter of the bandwidth-adjustable dual-passband filter according to the present application. Figure 3 Figure 8 is a structural schematic diagram of an adjustable band-stop sub-filter of the bandwidth-adjustable dual-passband filter according to the present application. Figure 9 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.3pF.

[0015] Figure 10 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.1pF. Figure 4 Figure 11 is a structural schematic diagram of a bandwidth-adjustable dual-passband filter according to the present application. Figure 12 is a structural schematic diagram of a band-pass sub-filter of the bandwidth-adjustable dual-passband filter according to the present application.

[0016] Figure 13 is a structural schematic diagram of an adjustable band-stop sub-filter of the bandwidth-adjustable dual-passband filter according to the present application. Figure 5 Figure 14 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.3pF. Figure 15 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter according to the present application when the capacitance value is 0.1pF.

[0017] In the drawings: 100 is a bandwidth-adjustable dual-passband filter, 101 is an input microstrip, 102 is a band-pass sub-filter, 103 is a cascaded microstrip, 104 is an adjustable band-stop sub-filter, 105 is an output microstrip, 106 is a 1 / 4 wavelength short-circuit line, 107 is a 1 / 2 wavelength main transmission line, 108 is a 1 / 2 wavelength resonator with a variable capacitance at a finger end, 109 is a zigzag microstrip, 110 and 111 are adjustable capacitors, 112 is a ground microstrip, 113 is a 1 / 4 wavelength main transmission line, 200 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter 100 when the capacitance value is 0.3pF, and 300 is a frequency response curve diagram of the bandwidth-adjustable dual-passband filter 100 when the capacitance value is 0.1pF. (V) DETAILED DESCRIPTION

[0018] Embodiment 1: A bandwidth-adjustable dual-passband filter 100, comprising an input microstrip 101, a band-pass sub-filter 102, a cascaded microstrip 103, an adjustable band-stop sub-filter 104, an output microstrip 105, characterized in that the band-pass sub-filter 102 and the adjustable band-stop sub-filter 104 are connected together through the cascaded microstrip 103, the band-pass sub-filter 102 is composed of a 1 / 4 wavelength short-circuit line 106 and a 1 / 2 wavelength main transmission line 107 in cascade, the adjustable band-stop sub-filter 104 is composed of a 1 / 2 wavelength resonator 108 with a variable capacitance loaded at the finger end and a 1 / 4 wavelength main transmission line 113 coupled together, the 1 / 2 wavelength resonator 108 with a variable capacitance loaded at the finger end is composed of a zigzag microstrip 109, two variable capacitors 110 and 111, and a ground microstrip 112, and the working frequency of the adjustable band-stop sub-filter 104 is located within the passband of the band-pass sub-filter 102.

[0019] The bandwidth-adjustable dual-passband filter 100, characterized in that the band-pass sub-filter 102, the 1 / 4 wavelength short-circuit line 106 and the 1 / 2 wavelength main transmission line 107 are alternately cascaded in whole 17, of which the 1 / 4 wavelength short-circuit line 106 is 9 and the 1 / 2 wavelength main transmission line 107 is 8.

[0020] The bandwidth-adjustable dual-passband filter 100, characterized in that the adjustable band-stop sub-filter 104, the 1 / 4 wavelength main transmission line 113 is connected together in cascade, the 1 / 2 wavelength resonator 108 with a variable capacitance loaded at the finger end is gap-coupled with the 1 / 4 wavelength main transmission line 113 in whole 10, of which the 1 / 2 wavelength resonator 108 with a variable capacitance loaded at the finger end is 5 and the 1 / 4 wavelength main transmission line 113 is 5.

[0021] The bandwidth-adjustable dual-passband filter 100, characterized in that the input microstrip 101 is directly excited by being connected to one end of the band-pass sub-filter 102.

[0022] The bandwidth-adjustable dual-passband filter 100, characterized in that the output microstrip 106 is directly excited by being connected to one end of the adjustable band-stop sub-filter 104.

Claims

1. A bandwidth-adjustable dual-passband filter comprising an input microstrip, a bandpass sub-filter, a cascaded microstrip, an adjustable bandstop sub-filter, an output microstrip, characterized in that, The band-pass sub-filter and the adjustable band-stop sub-filter are connected together through cascaded microstrips, the band-pass sub-filter is composed of 1 / 2 wavelength main transmission lines and 1 / 4 wavelength short-circuit lines in cascade, the adjustable band-stop sub-filter is composed of 1 / 4 wavelength main transmission lines and 1 / 2 wavelength resonators with variable capacitors loaded on the tips in coupling, the 1 / 2 wavelength resonator with variable capacitors loaded on the tips is composed of one zigzag microstrip, two variable capacitors and a ground microstrip, and the working frequency of the adjustable band-stop sub-filter is located in the passband of the band-pass sub-filter.

2. The bandwidth-adjustable dual-passband filter according to claim 1, wherein, The 1 / 2 wavelength main transmission lines and the 1 / 4 wavelength short-circuit lines of the band-pass sub-filter are alternately connected in cascade, and the total number is 5-50.

3. The bandwidth-adjustable dual-passband filter according to claim 1, wherein, The 1 / 4 wavelength main transmission lines of the adjustable band-stop sub-filter are connected together through cascade, the 1 / 2 wavelength resonators with variable capacitors loaded on the tips are gap-coupled with the 1 / 4 wavelength main transmission lines, and the total number is 5-50.

4. The bandwidth-adjustable dual-passband filter according to claim 1, wherein, The input microstrip is connected with one end of the band-pass sub-filter to produce direct excitation.

5. The bandwidth-adjustable dual-passband filter according to claim 1, wherein, The output microstrip is connected with one end of the adjustable band-stop sub-filter to produce direct excitation.

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